CarotenoidIntakeandCirculatingCarotenoidsAre InverselyAssociatedwiththeRiskofBladder Cancer:ADose-ResponseMeta-analysis

Abstract

Some evidence indicates that carotenoids may reduce the risk of bladder cancer (BC), but the association is unclear. We conducted a systematic review and meta-analysis of case-control and cohort studies investigating the relation between carotenoid intake or circulating carotenoid concentrations and BC risk in men and women. All relevant epidemiologic studies were identified by a search of PubMed and Scopus databases, andtheCochraneLibraryfrominceptiontoApril2019withnorestrictions.Arandom-effectsmodelwasusedtocalculatepooledRRsandtheir95% CIsacrossstudiesforhighcomparedwithlowcategoriesofintakeorcirculatingconcentrations.Wealsoperformedadose-responsemeta-analysis usingtheGreenlandandLongneckermethodandrandom-effectsmodels.Atotalof22studiesinvolving516,740adultswereincludedinthemetaanalysis. The pooled RRs of BC for the highest compared with the lowest category of carotenoid intake and circulating carotenoid concentrations were0.88(95%CI:0.76,1.03)and0.36(95%CI:0.12,1.07),respectively.ThepooledRRofBCforthehighestcomparedwithlowestcirculatinglutein andzeaxanthinconcentrationswas0.53(95%CI:0.33,0.84).Dose-responseanalysisshowedthatBCriskdecreasedby42%forevery1mgincrease in daily dietary β-cryptoxanthin intake (RR: 0.58; 95% CI: 0.36, 0.94); by 76% for every 1 μmol/L increase in circulating concentration of α-carotene (RR:0.24;95%CI:0.08,0.67);by27%forevery1 μmol/Lincreaseincirculatingconcentrationof β-carotene(RR:0.73;95%CI:0.57,0.94);andby56% forevery 1 μmol/Lincreaseincirculatingconcentrationsoflutein andzeaxanthin (RR: 0.44;95% CI:0.28, 0.67). Dietary β-cryptoxanthinintakeand circulatingconcentrationsofα-carotene,β-carotene,andluteinandzeaxanthinwereinverselyassociatedwithBCrisk.Theprotocolwasregistered atPROSPEROasCRD42019133240